The present invention relates to methods for making semiconductor devices, in particular, semiconductor devices that include high-k gate dielectric layers.
MOS field-effect transistors with very thin silicon dioxide based gate dielectrics may experience unacceptable gate leakage currents. Forming the gate dielectric from certain high-k dielectric materials, instead of silicon dioxide, can reduce gate leakage. Such a dielectric may not, however, be compatible with polysiliconxe2x80x94the preferred material for making the device""s gate electrode.
If such a high-k film comprises an oxide, it may manifest oxygen vacancies and excess impurity levels. Oxygen vacancies may permit undesirable interaction between the high-k film and the gate electrode. When the gate electrode comprises polysilicon, such interaction may after the electrode""s workfunction or cause the device to short through the dielectric. If the process for forming the high-k film uses a metal chloride precursor, residual chlorine may adversely affect the device""s electrical properties.
Accordingly, there is a need for an improved process for making a semiconductor device that includes a high-k gate dielectric. There is a need for such a process for forming a very thin high-k gate dielectric that improves the interface between the high-k film and the gate electrode by minimizing oxygen vacancies in the high-k film. There is a need for a process for forming a high-k gate dielectric with acceptable impurity levels. The method of the present invention provides such a process.